Solar storms or geomagnetic storms pose a dangerous threat to our technology-dependent society. Scientists say that solar storms can directly disrupt the planet's communication and power networks, adding that such disturbances have previously occurred.

The Colaba observatory in India once detected the largest, most powerful solar storm ever recorded, leading to power outages in telegraph system facilities all over North America and Europe in 1859. The Carrington event, named after astronomer Richard Carrington who witnessed the phenomenon, was seen even at places in low latitudes such as the Caribbean Sea and Madrid.

Meanwhile, in 2003, The Tihany Magnetic Observatory in Hungary once recorded a solar storm comparable to the Carrington Event. Astronomers called it the Halloween Solar Storm and other observatories were completely unaware of its occurrence.

Scientists now believe that most detection systems fail to spot geomagnetic perturbations from the Sun. Astronomers from the University of Alcalá explained that the current indices used by scientists to assess solar storms may have had resulted to miscalculations.

Scientists use the Dst (Disturbance storm time) to collect the average data recorded at observatories in San Juan (Puerto Rico), Honolulu (Hawaii, USA), Kakioka (Japan) and Hermanus (South Africa) every hour. Another version is the SYM-H (Symmetric disturbance field in H), which examines the horizontal part of the planet's magnetic field.

All these data are evaluated and compared in a study published (PDF) in the Journal of Space Weather and Space Climate. Researchers noticed the similarities in both events. They believed that an analysis of the Halloween Solar Storm event could result to a re-interpretation of the Carrington event. They also believed that scientists may have incurred errors in calculating the Dst.

The team said that the errors may have occurred when scientists measured the positive and negative magnetic perturbations from the Sun. These scientists failed to see that the combination of these two would result in the disappearance of the true magnetic disturbance.

The contribution of field-aligned currents to the measurement of the Earth's horizontal component (H) may have also increased the drop in H recorded at the incident in Colaba. Scientists believe that solar storms depend on the Earth's longitude, but other scientists disagree, saying that it is affected by the latitude.

Consuelo Cid, lead researcher from Spain, said that there is a need to develop local indices that are much more effective.

"A Carrington-like event may occur more often than we expect; actually, it might have already happened without us even realizing it," she said.

Cid and her colleagues created the Local Disturbance index for Spain (LDiñ), which is specifically made for measuring the perturbations in the area. The calculations are based on the data taken at the observatory in San Pablo, Toledo.

Cid added that a similar index may be applied in neighboring countries such as France, Italy and Portugal, and that adjusted indices could even be developed for individual regions worldwide.

Cid hopes that their team's collaboration with Red Eléctrica Española, the national power grid company in Spain, will allow them to work with other electric companies.

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